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Woodboss

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    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    2 hours ago, Stormhog said:

    Another pic, this one of the shelf cloud arriving last night, from Seaford. I have a few pictures taken over a couple of minutes, so I'll make a timelapse and post it when it's finished.

    DSC_5465.png

    This is absolutely unreal, great shot mate! I was in Shoreham and got under a direct hit and the lightning there went berserk very quickly. Could see the shelf heading towards the seaford area from where I was!

    • Like 1

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    54 minutes ago, Flash bang flash bang etc said:

    Wisley Airfield is right by the A3 interchange (junction 10 I think). You have to park your car at the end of a small road and walk over a log but when you’re on the airfield itself it’s very open and away from major lights. The A3 noise is a bit of an issue - but it’s a lovey spot and I can imagine pretty good for a night like tonight.

    Another option is Butser Hill but that’s very central along the coast so probably too far west…

    I was thinking of Leith Hill looking to the south… or that car park near Epsom Racecourse - but it will be full of stoners and/or doggers, and the light pollution there isn’t great

    Devil's dyke just north of Hove is a great spot if you can get there buddy, always my first port of call with these situations as visuals are awesome.

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    23 minutes ago, Supacell said:

    There are a lot of accidents this evening 🤦‍♂️

    M1 closed southbound

    M11 closed southbound

    M25 long delays over Queen Elizabeth ll Bridge

    Essentially means I'm going to struggle to get south. I really want to get south as want to catch these storms before daylight tomorrow. So thinking the south coast is my best bet. 

    South coast would be your best bet I would say, could go anti clock round the m25 if you can and then you'll have the a3 down to Portsmouth,m23 down to Brighton,a22 down to Eastbourne or a21 down to Hastings but the latter 2 increases the miles a fair bit if you don't go over the bridge.

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    7 minutes ago, lottiekent said:

    Camping at the Warren or Little Switzerland? Brilliant storm watching from both of those if you are!

    The Warren for one night and wild camp for 2 night's potentially capel le ferne cliffs. If we leave tonight then likely a night in the car as its far safer on high ground than the tent! Thanks for letting me know both have good visuals for storms and good luck with getting a storm in your neck of the woods 👍!

    • Like 1

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    57 minutes ago, Supacell said:

    Definitely. Although to be fair it was raining at home. 

    Currently at Bishops Stortford trying to decide my next move. M11 is also shut (as is the M1) but can still get to the M25 and on to Kent by going round the closure.

    Alternatively I could stick with the Essex coast, which is closer.

    @Peachy good luck tonight, nice to see I'm not the only one willing to drive a long distance to see a storm 👍

    Good luck tonight supacell, the miles and dedication you put in are second to none and I hope you hit the jackpot mate!

    • Like 1
    • Thanks 1

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    11 minutes ago, Lu. said:

    I’m being incredibly indecisive right now, my plans were to go to Worthing - I’ve had my power nap. But my gut feeling is to maybe wait it out here at Southsea 😅🤷🏻‍♀️

    Worthing might not be a bad shout to be fair Lu, I'm thinking of starting out at Shoreham just east of there or my usual spot at devil's dyke on top of the downs just inland. Visuals up there are very good out to sea and also inland too👍! Good luck.

    • Like 1

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    Evening all hope everyone is well. As we are all aware there is a potentially interesting night now upon us with most models hinting at quite a lively night for some of us in the south east. I will certainly be out for a chase tonight as I'm heading to Folkstone for a camping trip with my 9 year old son and we are packed and ready to go and should it kick off tonight we can be on the road and attempt to get underneath the best areas if it decides to turn up! Good luck to all who are chasing tonight and let's hope we get some pyrotechnics in the skies! Currently 21 degrees here in Hassocks with some accas starting to move in, it's certainly feeling pretty ripe and my confidence is increasing so all eyes on the skies and the radar for me now. Good luck everyone.

    • Like 2

    Storms and Convective discussion - 1st August 2022 onwards

    in Storms & Severe Weather

    Posted

    5 hours ago, BrickFielder said:

    Usual warnings on this information that I simplify things and don't exactly follow the rules so this will be a flavour of things rather than some of the very good technical explanations on the internet from professional meteorologists (My interpretation should be taken with a pinch of salt). Maybe somebody will do a proper pinned post of this but in the meantime check Nick's very good pinned guide to thunderstorms in the UK which covers many of the ideas which about SkewTs.

    SkewT Diagrams are usually seen with respect to soundings. Here a weather balloon is released to rise through the atmosphere and the temperature, dewpoint, wind speed and wind direction are recorded at different levels as the balloon rises and then plotted on the SkewT diagram. From this information you get a snapshot of the air conditions and this is useful for predicting weather conditions downwind. For example the Nottingham soundings are sometimes useful for weather prediction later in the Netherlands or Germany. The only upstream sounding for the UK is Castor Bay in Ireland which tends to be useful for Scotland and Norway. UK weather models rely heavily on Satellite monitoring which give a good idea of the air conditions upwind but has some limitations. What I tend to have a quick look at is the forecast (predicted) SkewTs and because they are not based on real measured conditions I often take certain liberties just to get a rough feel of conditions. 
     The types of things I can see from the diagrams is how humid air (dewpoint too close to temperature at any height may mean messy convection), is convection possible, is there cooler air aloft making things more unstable, is there wind shear which could enhance storms or make them long lived, is there CIN or a CAP stopping convection and how low cloud bases are and how high cloud tops are. Looking at a forecast SkewT I have numbered some features and lines and will try to explain what they are and how I interpret things (shortcuts included) 
    sound-Caerdydd-Cardiff.thumb.png.b1212891c082f8aa5e369e8e3342cca7.png

    1. Winds going up through the atmosphere giving direction and strength (number of barbs). The more winds turn with height and more speed difference there is between the surface and upper levels (Wind shear) the more severe a storm might be.
    2. Isotherm lines (blue) and saturation mixing ratio lines (yellow dotted) are used to calculate the lcl and ccl(cloud base). Everywhere along an isotherm has the same temperature.
    3. Saturated adiabatics (green dashed lines) (dry adiabatics are the red lines but I don't really use them but should). As moist air rises it condenses out into cloud and becomes cooler. If the air is still warmer than the surrounding air after the cooling it will continue to rise. So this line is the rate at which air cools as it goes up and produces cloud.
    4. The actual or forecast temperature of air at a particular height above the ground. If the temperature drops rapidly (lapse rate) between the surface and high up at the tropopause due to cooler air aloft and drops quicker than the saturated adiabatic rate then air will rise and produce cloud (convection) up to a point where warmer air is encountered. There other mechanisms for example fronts that produce cloud so it is not the complete story.
    5. Dewpoint temperature which is a measure of humidity of the air. If the dewpoint and temperature are very close together then humidity is likely close to 100% and cloud will form at that level which might affect temperatures at the surface and lapse rates. Humidity at the surface will tend to dictate cloud base levels and whether any moisture is available to form clouds.
    6. This is a line I add myself to guess at the cloud base level. It should be parallel to the saturation mixing ratio but I tend to use the isotherm line. To do this properly you should draw a line from the surface temperature parallel to the dry adiabatic (red lines) and draw a line from the surface dew point parallel to the saturated adiabatic (yellow dashed lines). This is the place where a surface parcel of air will begin condense out into cloud provided the meeting point of the two lines is above the temperature line.(This is where I take a bit of a rough shortcut)
    7. This a line also added by myself which estimates the level of free convection (cloud top height). This should be a curved line from the intersection point determined by 6 (cloud base level) following the saturated adiabatic until it intersects with the temperature line. The larger the area between this line and the temperature line the more unstable the atmosphere is.
    8. Things like elevated convection (The lines I have drawn don't work) and other scenarios may show up here. The higher the cape number the more unstable and stronger storms will happen. Li represents the lapse rate and the higher it is the stronger storms will be. CIN is a rating of prevention of convection and the higher the number the less likely storms will occur. Pressure 1000mb tells you convection should be from the surface and not elevated.

    Strictly speaking the forecast SkewT shown may not lead to a storm due to the CIN level, but considering it is estimated from satellite images certain liberties when taken in conjunction with precipitation charts don't seem unreasonable.

    OK lets test out the theory on a forecast SkewT from tomorrow. (I will try do it properly for once - if I am interpreting the lines correctly)

    sound-London-24.thumb.png.e4447120ee656b9d4c8f729c0086bdb6.pngsound-London-edit.thumb.png.7141120eee68391725b5b8fcdaa6d203.png

    I can see the dewpoint line close to the temperature line at higher levels. This suggests convection might be embedded or very messy. There are very strong winds up near the tropopause which would suggest a jet stream (high fast winds) and cloud tops being spread quickly at higher levels. Wind speed and direction differences are not in the key areas to affect storm development much (lower and mid levels are more important). CIN of zero shows no prevention of convection and the 200 of Cape suggest weak instability and hence weak storms. 

    Looking at precipitation charts I would take that SkewT with a pinch of salt. Forecast SkewTs can be useful but need to be looked at in conjunction with other charts and the latest satellite imagery. Looks like multiple low level convergence zones occurring  which will tend to cause moisture pooling. Moisture pooling will increase the surface dewpoint and alter any forecast SkewT which does not take that into account. Wales looks like a good spot for storms again tomorrow but any cloud clearance may spark storms so keep an eye on the radar.

    nmmukprate.thumb.png.81662907948495d66eb7063432ab2b54.pngnmmukcloud.thumb.png.767c773ba86373aeacdce25d6a82c5b0.png

     

    Hopefully this might start to clear a little fog around SkewT's but it is not easy to explain and after a while it becomes instinctive for some storm enthusiasts and you begin to take liberties.

     

    This is a great post Brick and many thanks for taking the time to share this with the group. I'm still learning more about the science of it all so it's benefits me too. I have a lot of experience in the field and generally pick up situations quickly and I've been lucky enough to get under some absolutely monstrous storms over the years and had some very close calls which I have learnt from. There's a good few people in here with a lot of the technical knowledge and that's vital for the less experienced and betters the thread for all of us. Thanks again and keep the posts coming matey!

    Cheers.Neil.

     

     

    • Like 3

    Storms and Convective discussion - 1st May 2022 onwards

    in Storms & Severe Weather

    Posted

    5 hours ago, tomp456 said:

    Always expect the unexpected.

    As I said several pages ago, one of my all time favorite storms occurred  in 2014, around this time of year, NOTHING whatsoever was forecast. 

    I remember this one very well,not forecast at all yet I watched this steam up the adur valley from Shoreham when I was living in Henfield. Very strong gust front and prolific lightning with a CG strike just a few hundred yards away in the next field down. Was a fair amount of tree damage the following morning in the area!

    • Like 5
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